br Discussion Sato et al first reported
Discussion Sato et al.  first reported TCM in 1990, and thereafter, numerous cases were reported in the late 2000s. In 85% of the cases, TCM onset was preceded by an emotional or physical stress event, however, in 15% of the cases, the presence of a stress trigger could not be detected . Most patients with TCM are postmenopausal women between 62 and 75 years of age . Our patient was particularly nervous and had a low tolerance for stress. We speculated that the patient protracted acute A-1210477 that triggered TCM. The age and clinical course of our patient were consistent with typical TCM patterns. Several cases have been reported on TCM in patients with RVA pacing during the acute and chronic phase after pacemaker implantation. Kurisu et al.  described two cases that developed TCM with implantation of a permanent pacemaker. In their cases, the ECG showed ST-segment elevation. Abu Sham’a et al.  also reported a case with TCM which appeared following implantation of permanent pacemaker. The ECG of their case showed prolongation of the QTc interval up to 540ms and non-specific ST–T changes. Wissner et al.  described a case of TCM with intermittent pacemaker failure due to transient deterioration of the RVA pacing threshold. Their patient׳s ECG showed deep T-wave inversions in the inferior and precordial leads during atrial pacing, in addition to atrioventricular dissociation, complete heart block with junctional escape rhythm, and intermittent failure of the RVA pacing. Rorondi et al.  described a case of TCM in a patient with pacemaker syndrome. Initially, this patient׳s pacemaker was programmed to the DDDR mode at a lower heart rate of 60beats/min and no QTc prolongation or T-wave inversion was observed on the ECG. The pacemaker was reprogrammed to the VVI mode at a heart rate of 70beats/min, with hysteresis at 30beats/min, to maximize her own beats. After reprogramming of the pacing mode, the ECG showed sinus bradycardia at 33beats/min without pacing, QTc prolongation, and T-wave inversions in the inferior and precordial leads. T-wave inversion is frequently detected after RVA pacing as cardiac memory. Therefore, it may be difficult to differentiate whether their two patient׳s T-wave inversions were due to cardiac memory or TCM. Although QTc prolongation and T-wave inversions during RVA pacing have only been previously reported by Chauhan et al. , the QTc prolongation and T-wave inversions were not significant.
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Introduction Implantable cardioverter defibrillators (ICD) are effective in reducing mortality in patients with left ventricular dysfunction. Previous studies have shown that an estimated 12–21% of ICD patients receive an inappropriate shock [1–3], which is mainly caused by an erroneous diagnosis of supraventricular tachycardia (SVT) or oversensing . Inappropriate ICD shocks cause left ventricular (LV) dysfunction and increase the risk of mortality. Furthermore, patients receiving inappropriate ICD shocks have an impaired quality of life (QOL) . Although various tachycardia detection algorithms to avoid inappropriate ICD shock are currently available, they are limited by several issues, which need to be addressed [6,7]. The Wavelet™ (Medtronic Inc., MN, USA) is one of the morphology discrimination algorithms currently available for detecting ventricular tachycardia (VT) . This system automatically collects and updates the instrinsic rhythm template electrograms (EGMs) (rates <100bpm) recorded between the generator (Can) and the right ventricular (RV) coil (Can-RV coil) or between the superior vena cava (SVC) coil and the RV coil (SVC coil-RV coil). In response to the detection of tachycardia, the system compares baseline rhythm and recorded tachycardia EGMs. When at least 3 of the last 8 consecutive beats exceed a programmable match threshold (nominally 70%), the rhythm is classified as SVT and no ICD shock is delivered. In contrast, if the matching score is lower than the threshold, the Wavelet recognizes the rhythm as ventricular tachycardia (VT), and thus initiates an ICD shock.